[ 485 3 
fpedt fo accurate as I could wifh, I am fully per- 
fuaded, that fuch experiments, as are carefully made 
with it, may be depended upon, as very near the 
truth. Having made a great variety of experiments 
with this inftrument upon bars of different metals, as 
ne'arly of the fame dimenfions as poffible, I found, 
upon a medium, their feveral expanfions by the fame 
degree of heat to be as follows : 
Gold Silver Brafs Copper Iron Steel Lead 
71 I0 3 95 8 9 60 5 6 14 9 
And as I found fo great a difference between the ex- 
panfion of brafs and iron, I immediately determined 
to make a pendulum after the manner above de- 
fcribed, compofed of thofe two metals, and likewife 
order’d a clock to be made, with the utmoft care 
and exaCtnefs ; and, as I then apprehended, with 
fome confiderable improvements, with which I in- 
tended to make the experiments. Thefe were both 
finifhed in the beginning of the year 17385 and hav- 
ing no reafon to doubt of fuccels, I fhew’d the pen- 
dulum to the late Mr. Machin, and gave him a draw- 
ing and defcription of it, in order to its being com- 
municated to the Royal Society; but, as I have al- 
ready obferved, objections were made to it, of which 
the only one, that appeared to have any weight, was, 
that it had been found by experiment, that two bars 
of different metals, fcrew’d together, fo as to be in 
contaCt with each other, would not expand, regularly 
and fmoothly, but by jerks. In order to examine 
into the force of this objection, I directed two bars of 
equal dimenfions to be made, one of brafs, the other 
of iron, of about two feet in length, fatten'd together 
after the fame manner, as the two rods of the 
pendulum, 
